Commodity Derivative Positions (Detail) $ in Thousands	6 Months Ended
Jun. 30, 2017 USD ($) bbl $ / bbl	Dec. 31, 2016 USD ($)
Derivative Instruments Related to Oil and Gas Production [Line Items]
Derivative Liability	$ 90	$ 27,369
Settlement Agreement [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Fair Value Asset	457,245
Fair Value Liability
Crude Oil \| Third Quarter 2017 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day \| bbl	4,408
Derivative, Swap Type, Average Fixed Price \| $ / bbl	48.59
Fair Value Asset	$ 903,636
Fair Value Liability	$ 0
Crude Oil \| Fourth Quarter 2017 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day \| bbl	4,408
Derivative, Swap Type, Average Fixed Price \| $ / bbl	48.59
Fair Value Asset	$ 591,129
Fair Value Liability	$ 0
Crude Oil \| First Quarter 2018 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day \| bbl	3,476
Derivative, Swap Type, Average Fixed Price \| $ / bbl	49.10
Fair Value Asset	$ 419,761
Fair Value Liability	$ 0
Crude Oil \| Second Quarter 2018 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day \| bbl	3,476
Derivative, Swap Type, Average Fixed Price \| $ / bbl	49.10
Fair Value Asset	$ 299,826
Fair Value Liability	$ 0
Crude Oil \| Third Quarter 2018 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day \| bbl	3,476
Derivative, Swap Type, Average Fixed Price \| $ / bbl	49.10
Fair Value Asset	$ 193,534
Fair Value Liability	$ 0
Crude Oil \| Fourth Quarter 2018 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day \| bbl	3,476
Derivative, Swap Type, Average Fixed Price \| $ / bbl	49.10
Fair Value Asset	$ 82,328
Fair Value Liability	$ 0
Crude Oil \| First Quarter 2019 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day \| bbl	2,916
Derivative, Swap Type, Average Fixed Price \| $ / bbl	49.75
Fair Value Asset	$ 160,594
Fair Value Liability	$ 0
Crude Oil \| Second Quarter 2019 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day \| bbl	2,916
Derivative, Swap Type, Average Fixed Price \| $ / bbl	49.75
Fair Value Asset	$ 88,824
Fair Value Liability	$ 0
Crude Oil \| Third Quarter 2019 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day \| bbl	2,916
Derivative, Swap Type, Average Fixed Price \| $ / bbl	49.75
Fair Value Asset	$ 24,775
Fair Value Liability	$ 0
Crude Oil \| Fourth Quarter 2019 [Member]
Derivative Instruments Related to Oil and Gas Production [Line Items]
Instrument	Swaps
Notional Volume, per day \| bbl	2,916
Derivative, Swap Type, Average Fixed Price \| $ / bbl	49.75
Fair Value Asset	$ 0
Fair Value Liability	$ 56,550

Aggregate notional amount of derivative expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
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Fair value as of the balance sheet date of derivative instrument not designated as hedging instrument and classified as an asset.

+ References

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-Name Accounting Standards Codification
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Description of the type of derivative instrument, such as a swap, forward, and option. Excludes the underlying risk of the instrument.

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